6.For security reasons, the network administrator needs to prevent pings into the corporate networks from hosts outside the internetwork. Which protocol should be blocked with access control lists?
A. IP
B. ICMP
C. TCP
D. UDP
Answer: B
解释一下:PING命令 利用ICMP协议的echo,和 echo-replay两个报文来检测链路是否连通的。所以如果要阻止PING的流量到网络,就只要过滤掉ICMP的应用就可以了。
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